This invention relates generally to variable resistance devices and, more particularly, to such devices that employ a resistance element with a surface that is traversed by a wiper contact.
Wiper contacts are used in a variety of variable resistance devices such as potentiometers, rheostats, etc. To provide and retain the electrical performance required, the wiper contacts used with such devices must possess a number of characteristics including resiliency, low contact resistance with high electrical conductivity and resistance to wear and corrosion. Because of these stringent requirements, platinum or other precious metal alloys are generally used for variable resistance wiper contacts. The high cost of such materials contribute substantially to the total cost of the complete device.
In the interest of economy, there have been proposed composite wiper contacts consisting of a contact tip formed of a precious metal and an elongated spring portion formed of Beryllium copper or the like. A composite wiper contact of this type is disclosed, for example, in U.S. Pat. No. 2,721,246. Although they reduce the overall cost of variable resistance devices, composite wiper contacts have not been used extensively because of various disadvantages including expensive production requirements, unreliability, poor electrical performance, etc.
The object of this invention, therefore, is to provide an improved, variable resistance device of the type employing a wiper contact.